Objects such as wafers are manufactured by highly complicated manufacturing processes. These manufacturing processes should be monitored in order to ensure the quality of the wafers.
Monitoring process may include (a) using an inspection tool for performing an inspection process to detect potential defects, and (b) using a review tool for performing a review of the potential defects.
The inspection tool may illuminate the object by one or more beams of electrons, ions or by one or more beams of optical, ultraviolet, deep ultraviolet or extreme ultraviolet radiation. The review tool usually illuminates the objects using one or more electron beams or one or more an ion beams.
Each tool of the inspection tool and the review tool may scan the object (or only parts of the object) by introducing a mechanical movement between the object and either the optical or electron optics.
The mechanical movement is usually introduced by a movable support module that may be a mechanical stage. The mechanical stage may be an XYZ stage that is configured to support the object and to move the object along imaginary X axis, Y axis and Z axis.
The mechanical stage location is monitored by X axis and Y axis laser interferometers.
It has been found that laser interferometer based monitoring does not provide adequate compensation for mechanical stage movement inaccuracies.
There is a growing need to provide a method for reducing the location errors in an inspection or review tool.